Process for the preparation of polyether polyols

ABSTRACT

The invention relates to a method for producing polyether carbonate polyols, wherein (i) in a first step a polyether carbonate polyol is produced from one or more H-functional starter substances, one or more alkylene oxides, and carbon dioxide in the presence of at least one DMC catalyst, and (ii) in a second step the polyether carbonate polyol is chain-extended with a mixture of at least two different alkylene oxides in the presence of at least one DMC catalyst. The invention further relates to polyether carbonate polyols that contain a terminal mixed block of at least two alkylene oxides and to a method for producing soft polyurethane foams, wherein a polyol component containing a polyether carbonate polyol according to the invention is used.

The present invention relates to a process for the preparation ofpolyethercarbonate polyols from one or more H-functional startersubstances, one or more alkylene oxides and carbon dioxide in thepresence of at least one double metal cyanide catalyst, thepolyethercarbonate polyols having a mixed block of at least two alkyleneoxides at the end of the chain, and to flexible polyurethane foamsobtainable therefrom.

The preparation of polyethercarbonate polyols by the catalytic reactionof alkylene oxides (epoxides) and carbon dioxide in the presence orabsence of H-functional starter substances (starters) has been studiedintensively for more than 40 years (e.g. Inoue et al., Copolymerizationof Carbon Dioxide and Epoxide with Organometallic Compounds; DieMakromolekulare Chemie 130, 210-220, 1969). This reaction, e.g. using anH-functional starter compound, is shown diagrammatically in Scheme (I),where R is an organic radical such as alkyl, alkylaryl or aryl, each ofwhich can also comprise heteroatoms such as O, S, Si, etc., and e and fare integers, and where the product shown here in Scheme (I) for thepolyethercarbonate polyol is only to be understood as meaning thatblocks with the indicated structure can in principle be found in thepolyethercarbonate polyol obtained, but that the sequence, number andlength of the blocks and the OH functionality of the starter can varyand are not limited to the polyethercarbonate polyol shown in Scheme(I). This reaction (cf. Scheme (I)) is ecologically very advantageousbecause it represents the conversion of a greenhouse gas like CO₂ to apolymer. The cyclic carbonate shown in Scheme (I) (e.g. propylenecarbonate for R═CH₃) is formed as a further product (actually aby-product).

Activation in terms of the invention is a step in which a fraction ofthe alkylene oxide compound, optionally in the presence of CO₂, is addedto the DMC catalyst and the addition of the alkylene oxide compound isthen interrupted; an evolution of heat, which can lead to a hotspot, isobserved due to a subsequent exothermic chemical reaction, and apressure drop in the reactor is observed due to the conversion ofalkylene oxide and optionally CO₂. The process step of activation is theperiod of time from the addition of the fraction of alkylene oxidecompound to the DMC catalyst, optionally in the presence of CO₂, up tothe start of the evolution of heat. In general, the activation step canbe preceded by a step for drying of the DMC catalyst and optionally thestarter at elevated temperature and/or reduced pressure, this dryingstep not being part of the activation step in terms of the presentinvention.

The formation of copolymers from epoxides (e.g. propylene oxide) andcarbon dioxide has been known for a long time. Thus, for example, U.S.Pat. No. 4,500,704 describes the copolymerization of carbon dioxide andpropylene oxide using DMC catalysts. In this case, for example, with astarter substance and 12.3 g (212 mmol) of propylene oxide in a reactorunder a carbon dioxide pressure of 48 bar, 71% of the propylene oxidewas converted after 48 hours at 35° C. Of the 150.5 mmol of propyleneoxide converted, 27 mmol (18%) reacted to give propylene carbonate, agenerally unwanted by-product.

WO-A 2008/058913 discloses a process for the preparation ofpolyethercarbonate polyols having a block of pure alkylene oxide units,especially a block of pure propylene oxide units, at the end of thechain. However, WO-A 2008/058913 does not disclose polyethercarbonatepolyols having a mixed block of at least two alkylene oxides at the endof the chain.

The object of the present invention was to provide polyethercarbonatepolyols that produce flexible polyurethane foams with an increasedcompressive strength and an increased tensile strength. In practice, aflexible polyurethane foam quality improved in this way has thetechnical advantage that said foams have an increased mechanicalload-bearing capacity.

It has now been found, surprisingly, that flexible polyurethane foamswith an increased compressive strength and an increased tensile strengthresult from polyethercarbonate polyols having a mixed block of at leasttwo alkylene oxides at the end of the chain (“terminal mixed block”).The present invention thus provides a process for the preparation ofpolyethercarbonate polyols which is characterized in that

-   -   (i) in a first step a polyethercarbonate polyol is prepared from        one or more H-functional starter substances, one or more        alkylene oxides and carbon dioxide in the presence of at least        one DMC catalyst, and    -   (ii) in a second step the polyethercarbonate polyol chain is        extended with a mixture of at least two different alkylene        oxides in the presence of at least one DMC catalyst,        and in that the mixture of at least two different alkylene        oxides used in the second step (ii) is a mixture comprising        propylene oxide (PO) and ethylene oxide (EO) in a molar ratio        PO/EO of 15/85 to 60/40.

The present invention also provides a process for the production offlexible polyurethane foams wherein the starting material used is apolyol component (component A) comprising a polyethercarbonate polyolobtainable by a process which is characterized in that

-   -   (i) in a first step a polyethercarbonate polyol is prepared from        one or more H-functional starter substances, one or more        alkylene oxides and carbon dioxide in the presence of at least        one DMC catalyst, and    -   (ii) in a second step the polyethercarbonate polyol chain is        extended with a mixture of at least two different alkylene        oxides in the presence of at least one DMC catalyst,        and in that the mixture of at least two different alkylene        oxides used in the second step (ii) is a mixture comprising        propylene oxide (PO) and ethylene oxide (EO) in a molar ratio        PO/EO of 15/85 to 60/40.

The flexible polyurethane foams according to the invention preferablyhave a gross density according to DIN EN ISO 3386-1-98 in the range from≧10 kg/m³ to ≦150 kg/m³, preferably from ≧20 kg/m³ to ≦70 kg/m³, and acompressive strength according to DIN EN ISO 3386-1-98 in the range from≧0.5 kPa to ≦20 kPa (at 40% deformation after 4^(th) cycle).

Step (i):

The preparation of the polyethercarbonate polyol according to step (i)is preferably carried out by adding one or more alkylene oxides andcarbon dioxide, in the presence of at least one DMC catalyst, on to oneor more H-functional starter substances (“copolymerization”).

For example, the process for the preparation of polyethercarbonatepolyol according to step (i) is characterized in that

-   (α) the H-functional starter substance or a mixture of at least two    H-functional starter substances is taken and optionally water and/or    other highly volatile compounds are removed by raising the    temperature and/or reducing the pressure (“drying”), the DMC    catalyst being added to the H-functional starter substance or the    mixture of at least two H-functional starter substances before or    after drying,-   (β) for activation, a fraction (based on the total amount of    alkylene oxides used in the activation and copolymerization) of one    or more alkylene oxides is added to the mixture resulting from step    (α), it optionally being possible for this addition of an alkylene    oxide fraction to take place in the presence of CO₂, the hotspot    that occurs due to the subsequent exothermic chemical reaction    and/or a pressure drop in the reactor then being allowed to subside,    and it also being possible for the activation step (β) to be carried    out several times, and-   (γ) one or more alkylene oxides and carbon dioxide are added to the    mixture resulting from step (β), it being possible for the alkylene    oxides used in step (γ) to be identical to or different from the    alkylene oxides used in step (β).

In general, alkylene oxides (epoxides) having 2-24 carbon atoms can beused for the process according to the invention. Examples of alkyleneoxides having 2-24 carbon atoms are one or more compounds selected fromthe group comprising ethylene oxide, propylene oxide, 1-butene oxide,2,3-butene oxide, 2-methyl-1,2-propene oxide (isobutene oxide),1-pentene oxide, 2,3-pentene oxide, 2-methyl-1,2-butene oxide,3-methyl-1,2-butene oxide, 1-hexene oxide, 2,3-hexene oxide, 3,4-hexeneoxide, 2-methyl-1,2-pentene oxide, 4-methyl-1,2-pentene oxide,2-ethyl-1,2-butene oxide, 1-heptene oxide, 1-octene oxide, 1-noneneoxide, 1-decene oxide, 1-undecene oxide, 1-dodecene oxide, butadienemonoxide, isoprene monoxide, cyclopentene oxide, cyclohexene oxide,cycloheptene oxide, cyclooctene oxide, styrene oxide, methylstyreneoxide, pinene oxide, mono- or polyepoxidized fats as mono-, di- andtriglycerides, epoxidized fatty acids, C₁-C₂₄ esters of epoxidized fattyacids, epichlorohydrin, glycidol, glycidol derivatives such as methylglycidyl ether, ethyl glycidyl ether, 2-ethylhexyl glycidyl ether, allylglycidyl ether and glycidyl methacrylate, and epoxy-functionalalkoxysilanes such as 3-glycidyloxypropyltri-methoxysilane,3-glycidyloxypropyltriethoxysilane,3-glycidyloxypropyltripropoxy-silane,3-glycidyloxypropylmethyldimethoxysilane,3-glycidyloxypropylethyldi-ethoxysilane and3-glycidyloxypropyltriisopropoxysilane. The alkylene oxides used in step(i) are preferably ethylene oxide and/or propylene oxide, especiallypropylene oxide.

Suitable H-functional starter substances which can be used are compoundswith H atoms that are active for alkoxylation. Examples of groups with Hatoms that are active for alkoxylation are —OH, —NH₂ (primary amines),—NH— (secondary amines), —SH and —CO₂H; —OH and —NH₂ are preferred and—OH is particularly preferred. Examples of H-functional startersubstances used are one or more compounds selected from the groupcomprising monohydric or polyhydric alcohols, polybasic amines,polyhydric thiols, amino alcohols, thio alcohols, hydroxy esters,polyether polyols, polyester polyols, polyesterether polyols,polyethercarbonate polyols, polycarbonate polyols, polycarbonates,polyethyleneimines, polyetheramines (e.g. so-called Jeffamine® fromHuntsman, such as D-230, D-400, D-2000, T-403, T-3000 or T-5000, orcorresponding products from BASF, such as polyetheramine D230, D400,D200, T403 or T5000), polytetrahydrofurans (e.g. PolyTHF® from BASF,such as PolyTHF® 250, 650S, 1000, 1000S, 1400, 1800 or 2000),polytetrahydrofuranamines (BASF product polytetrahydrofuranamine 1700),poly-etherthiols, polyacrylate polyols, castor oil, ricinoleic acidmono- or diglyceride, fatty acid monoglycerides, chemically modifiedfatty acid mono-, di- and/or triglycerides, and fatty acid C₁-C₂₄-alkylesters comprising an average of at least 2 OH groups per molecule.Examples of fatty acid C₁-C₂₄-alkyl esters comprising an average of atleast 20H groups per molecule are commercially available products suchas Lupranol Balance® (BASF AG), various types of Merginol® (HobumOleochemicals GmbH), various types of Sovermol® (Cognis Deutschland GmbH& Co. KG) and various types of Soyol® TM (USSC Co.).

Monofunctional starter compounds which can be used are alcohols, amines,thiols and carboxylic acids. The following monofunctional alcohols canbe used: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol,2-butanol, tert-butanol, 3-buten-1-ol, 3-butyn-1-ol,2-methyl-3-buten-2-ol, 2-methyl-3-butyn-2-ol, propargyl alcohol,2-methyl-2-propanol, 1-tert-butoxy-2-propanol, 1-pentanol, 2-pentanol,3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-heptanol, 2-heptanol,3-heptanol, 1-octanol, 2-octanol, 3-octanol, 4-octanol, phenol,2-hydroxybiphenyl, 3-hydroxybiphenyl, 4-hydroxybiphenyl,2-hydroxypyridine, 3-hydroxypyridine, 4-hydroxypyridine. The followingmonofunctional amines are suitable: butylamine, tert-butylamine,pentylamine, hexylamine, aniline, aziridine, pyrrolidine, piperidine,morpholine. The following monofunctional thiols can be used:ethanethiol, 1-propanethiol, 2-propanethiol, 1-butanethiol,3-methyl-1-butanethiol, 2-butene-1-thiol, thiophenol. The followingmonofunctional carboxylic acids may be mentioned: formic acid, aceticacid, propionic acid, butyric acid, fatty acids such as stearic acid,palmitic acid, oleic acid, linoleic acid and linolenic acid, benzoicacid, acrylic acid.

Examples of polyhydric alcohols suitable as H-functional startersubstances are dihydric alcohols (e.g. ethylene glycol, diethyleneglycol, propylene glycol, dipropylene glycol, 1,3-propanediol,1,4-butanediol, 1,4-butenediol, 1,4-butynediol, neopentyl glycol,1,5-pentanediol, methylpentanediols (e.g. 3-methyl-1,5-pentanediol),1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol,bis-(hydroxymethyl)cyclohexanes (e.g.1,4-bis(hydroxymethyl)cyclohexane), triethylene glycol, tetraethyleneglycol, polyethylene glycols, dipropylene glycol, tripropylene glycol,polypropylene glycols, dibutylene glycol, polybutylene glycols);trihydric alcohols (e.g. trimethylolpropane, glycerol, trishydroxyethylisocyanurate, castor oil); tetrahydric alcohols (e.g. pentaerythritol);polyalcohols (e.g. sorbitol, hexitol, sucrose, starch, starchhydrolysates, cellulose, cellulose hydrolysates, hydroxy-functionalizedfats and oils, especially castor oil); and any modified products of theaforesaid alcohols comprising different amounts of ε-caprolactone.

The H-functional starter substances can also be selected from the classof substances comprising the polyether polyols, especially those with amolecular weight M_(n) ranging from 100 to 4000 g/mol. Preferredpolyether polyols are those made up of repeating ethylene oxide andpropylene oxide units, preferably with a proportion of 35 to 100% ofpropylene oxide units and particularly preferably with a proportion of50 to 100% of propylene oxide units. They can be random copolymers,gradient copolymers or alternating or block copolymers of ethylene oxideand propylene oxide. Examples of suitable polyether polyols made up ofrepeating propylene oxide and/or ethylene oxide units are theDesmophen®, Acclaim®, Arcol®, Baycoll®, Bayfill®, Bayflex®, Baygal®,PET° and Polyether® Polyols from Bayer MaterialScience AG (e.g.Desmophen® 3600Z, Desmophen® 1900U, Acclaim®Polyol 2200, Acclaim® Polyol40001, Arcol® Polyol 1004, Arcol® Polyol 1010, Arcol® Polyol 1030,Arcol® Polyol 1070, Baycoll® BD 1110, Bayfill® VPPU 0789, Baygal® K55,PET® 1004, Polyether® S180). Examples of other suitablehomo-polyethylene oxides are the Pluriol® E brands from BASF SE,examples of suitable homo-polypropylene oxides are the Pluriol® P brandsfrom BASF SE, and examples of suitable mixed copolymers of ethyleneoxide and propylene oxide are the Pluronic® PE or Pluriol® RPE brandsfrom BASF SE.

The H-functional starter substances can also be selected from the classof substances comprising the polyester polyols, especially those with amolecular weight M_(n) ranging from 200 to 4500 g/mol. The polyesterpolyols used are at least difunctional polyesters and preferably consistof alternating acid and alcohol units. Examples of acid components usedare succinic acid, maleic acid, maleic anhydride, adipic acid, phthalicanhydride, phthalic acid, isophthalic acid, terephthalic acid,tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalicanhydride or mixtures of said acids and/or anhydrides. Examples ofalcohol components used are ethanediol, 1,2-propanediol,1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol,1,6-hexanediol, 1,4-bis(hydroxymethyl)cyclohexane, diethylene glycol,dipropylene glycol, trimethylolpropane, glycerol, pentaerythritol ormixtures of said alcohols. If dihydric or polyhydric polyether polyolsare used as the alcohol component, polyesterether polyols are obtainedwhich can also be used as starter substances for preparing thepolyethercarbonate polyols. It is preferable to use polyether polyols ofM_(n)=150 to 2000 g/mol to prepare the polyesterether polyols.

Other H-functional starter substances which can be used arepolycarbonate polyols (e.g. polycarbonate diols), especially those witha molecular weight M_(n) ranging from 150 to 4500 g/mol, preferably from500 to 2500 g/mol, which are prepared e.g. by reacting phosgene,dimethyl carbonate, diethyl carbonate or diphenyl carbonate with di-and/or polyfunctional alcohols, polyester polyols or polyether polyols.Examples of polycarbonate polyols can be found e.g. in EP-A 1359177.Examples of polycarbonate diols which can be used are various types ofDesmophen® C from Bayer MaterialScience AG, such as Desmophen® C 1100 orDesmophen® C 2200.

In another embodiment of the invention, polyethercarbonate polyols canbe used as H-functional starter substances. The polyethercarbonatepolyols obtainable by the process according to the invention describedhere, after step (i), step (ii) or step (iii), are used in particular.These polyethercarbonate polyols used as H-functional starter substancesare previously prepared for this purpose in a separate reaction step.

The H-functional starter substances generally have a functionality (i.e.number of H atoms per molecule that are active for polymerization) of 1to 8, preferably of 2 or 3. The H-functional starter substances are usedeither individually or as a mixture of at least two H-functional startersubstances.

Preferred H-functional starter substances are alcohols of generalformula (II):

HO—(CH₂)_(x)—OH  (II)

where x is a number from 1 to 20, preferably an even number from 2 to20. Examples of alcohols of formula (II) are ethylene glycol,1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol and1,12-dodecanediol. Other preferred H-functional starter substances areneopentyl glycol, trimethylolpropane, glycerol, pentaerythritol, andreaction products of the alcohols of formula (II) with ε-caprolactone,e.g. reaction products of trimethylolpropane with ε-caprolactone,reaction products of glycerol with s-caprolactone and reaction productsof pentaerythritol with ε-caprolactone. Other H-functional startersubstances which are preferably used are water, diethylene glycol,dipropylene glycol, castor oil, sorbitol, and polyether polyols made upof repeating polyalkylene oxide units.

Particularly preferably, the H-functional starter substances are one ormore compounds selected from the group comprising ethylene glycol,propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol,1,5-pentanediol, 2-methylpropane-1,3-diol, neopentyl glycol,1,6-hexanediol, diethylene glycol, dipropylene glycol, glycerol,trimethylolpropane and di- and trifunctional polyether polyols, thepolyether polyol being made up of a di- or tri-H-functional startersubstance and propylene oxide or a di- or tri-H-functional startersubstance, propylene oxide and ethylene oxide. The polyether polyolspreferably have a molecular weight M_(n) ranging from 62 to 4500 g/moland a functionality of 2 to 3, especially a molecular weight M_(n)ranging from 62 to 3000 g/mol a functionality of 2 to 3.

The polyethercarbonate polyols are prepared by the catalytic addition ofcarbon dioxide and alkylene oxides on to H-functional startersubstances. In terms of the invention, “H-functional” is understood asmeaning the number of H atoms per molecule of starter compound that areactive for alkoxylation.

DMC catalysts for use in the homopolymerization of epoxides are known inprinciple from the state of the art (cf., for example, U.S. Pat. No.3,404,109, U.S. Pat. No. 3,829,505, U.S. Pat. No. 3,941,849 and U.S.Pat. No. 5,158,922). DMC catalysts described e.g. in U.S. Pat. No.5,470,813, EP-A 700 949, EP-A 743 093, EP-A 761 708, WO 97/40086, WO98/16310 and WO 00/47649 have a very high activity in thehomopolymerization of epoxides and enable polyether polyols to beprepared with very low catalyst concentrations (25 ppm or less), so itis generally no longer necessary to separate the catalyst from thefinished product. Typical examples are the highly active DMC catalystsdescribed in EP-A 700 949, which, in addition to a double metal cyanidecompound (e.g. zinc hexacyanocobaltate(III)) and an organic complexingligand (e.g. tert-butanol), also comprise a polyether with anumber-average molecular weight greater than 500 g/mol.

The DMC catalysts are obtained by a process in which

-   (a) in the first step, an aqueous solution of a metal salt is    reacted with an aqueous solution of a metal cyanide salt in the    presence of one or more organic complexing ligands, e.g. an ether or    alcohol,-   (b) in the second step, the solid is separated from the suspension    obtained in (i) by known techniques (such as centrifugation or    filtration),-   (c) optionally, in a third step, the isolated solid is washed with    an aqueous solution of an organic complexing ligand (e.g. by    resuspension and then re-isolation by filtration or centrifugation),    and-   (d) the solid obtained is then dried, optionally after    pulverization, at temperatures generally of 20-120° C. and at    pressures generally of 0.1 mbar to normal pressure (1013 mbar),    one or more organic complexing ligands, preferably in excess (based    on the double metal cyanide compound), and optionally other    complexing components, being added in the first step or immediately    after the precipitation of the double metal cyanide compound (second    step).

The double metal cyanide compounds comprised in the DMC catalysts arethe reaction products of water-soluble metal salts and water-solublemetal cyanide salts. For example, an aqueous solution of zinc chloride(preferably in excess, based on the metal cyanide salt, e.g. potassiumhexacyanocobaltate) and potassium hexacyanocobaltate are mixed anddimethoxyethane (glyme) or tert-butanol (preferably in excess, based onzinc hexacyanocobaltate) is then added to the suspension formed.

Metal salts suitable for preparing the double metal cyanide compoundspreferably have general formula (III):

M(X)_(n)  (III)

whereM is selected from the metal cations Zn²⁺, Fe²⁺, Ni²⁺, Mn²⁺, Co²⁺, Sr²⁺,Sn²⁺, Pb²⁺ and Cu²⁺, M preferably being Zn²⁺, Fe²⁺, Co²⁺ or Ni²⁺;X are one or more (i.e. different) anions, preferably an anion selectedfrom the group comprising halides (i.e. fluoride, chloride, bromide,iodide), hydroxide, sulfate, carbonate, cyanate, thiocyanate,isocyanate, isothiocyanate, carboxylate, oxalate and nitrate;n is 1 when X=sulfate, carbonate or oxalate; andn is 2 when X=halide, hydroxide, carboxylate, cyanate, thiocyanate,isocyanate, isothiocyanate or nitrate,or suitable metal salts have general formula (IV):

M_(r)(X)₃  (IV)

whereM is selected from the metal cations Fe³⁺, Al³⁺, Co³⁺ and Cr³⁺;X are one or more (i.e. different) anions, preferably an anion selectedfrom the group comprising halides (i.e. fluoride, chloride, bromide,iodide), hydroxide, sulfate, carbonate, cyanate, thiocyanate,isocyanate, isothiocyanate, carboxylate, oxalate and nitrate;r is 2 when X=sulfate, carbonate or oxalate; andr is 1 when X=halide, hydroxide, carboxylate, cyanate, thiocyanate,isocyanate, isothiocyanate or nitrate,or suitable metal salts have general formula (V):

M(X)_(s)  (V)

whereM is selected from the metal cations Mo⁴⁺, V⁴⁺ and W⁴⁺;X are one or more (i.e. different) anions, preferably an anion selectedfrom the group comprising halides (i.e. fluoride, chloride, bromide,iodide), hydroxide, sulfate, carbonate, cyanate, thiocyanate,isocyanate, isothiocyanate, carboxylate, oxalate and nitrate;s is 2 when X=sulfate, carbonate or oxalate; ands is 4 when X=halide, hydroxide, carboxylate, cyanate, thiocyanate,isocyanate, isothiocyanate or nitrate,or suitable metal salts have general formula (VI):

M(X)_(t)  (VI)

whereM is selected from the metal cations Mo⁶⁺ and W⁶⁺;X are one or more (i.e. different) anions, preferably an anion selectedfrom the group comprising halides (i.e. fluoride, chloride, bromide,iodide), hydroxide, sulfate, carbonate, cyanate, thiocyanate,isocyanate, isothiocyanate, carboxylate, oxalate and nitrate;t is 3 when X=sulfate, carbonate or oxalate; andt is 6 when X=halide, hydroxide, carboxylate, cyanate, thiocyanate,isocyanate, isothiocyanate or nitrate.

Examples of suitable metal salts are zinc chloride, zinc bromide, zinciodide, zinc acetate, zinc acetylacetonate, zinc benzoate, zinc nitrate,iron(II) sulfate, iron(II) bromide, iron(II) chloride, iron(III)chloride, cobalt(II) chloride, cobalt(II) thiocyanate, nickel(II)chloride and nickel(II) nitrate. It is also possible to use mixtures ofdifferent metal salts.

Metal cyanide salts suitable for preparing the double metal cyanidecompounds preferably have general formula (VII):

(Y)_(a)M′(CN)_(b)(A)_(c)  (VII)

whereM′ is selected from one or more metal cations from the group comprisingFe(II), Fe(III), Co(II), Co(III), Cr(II), Mn(II), Mn(III), Ir(III),Ni(II), Ru(II), V(IV) and V(V), M′ preferably being one or more metalcations from the group comprising Coal), Co(III), Fe(II), Fe(III),Cr(III), Ir(III) and Ni(II);Y is selected from one or more metal cations from the group comprisingalkali metals (i.e. Li⁺, Na⁺, K⁺, Rb⁺) and alkaline earth metals (i.e.Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺);A is selected from one or more anions from the group comprising halides(i.e. fluoride, chloride, bromide, iodide), hydroxide, sulfate,carbonate, cyanate, thiocyanate, isocyanate, isothiocyanate,carboxylate, azide, oxalate and nitrate; and a, b and c are integers,the values of a, b and c being chosen so that the metal cyanide salt iselectronically neutral; a is preferably 1, 2, 3 or 4; b is preferably 4,5 or 6; c preferably has the value 0.

Examples of suitable metal cyanide salts are sodiumhexacyanocobaltate(III), potassium hexacyanocobaltate(III), potassiumhexacyanoferrate(II), potassium hexacyanoferrate(III), calciumhexacyanocobaltate(III) and lithium hexacyano-cobaltate(III).

Preferred double metal cyanide compounds comprised in the DMC catalystsare compounds of general formula (VIII):

M_(x)[M′_(x′)(CN)_(y)]_(z)  (VI)

whereM is as defined in formulae (III) to (VI);M′ is as defined in formula (VII); andx, x′, y and z are integers and are chosen so that the double metalcyanide compound is electronically neutral.

Preferably:

x=3, x′=1, y=6 and z=2;

M=Zn(II), Fe(II), Co(II) or Ni(II); and M′=Co(III), Fe(III), Cr(III) or

Examples of suitable double metal cyanide compounds a) are zinchexacyano-cobaltate(III), zinc hexacyanoiridate(III), zinchexacyanoferrate(III) and cobalt(II) hexacyanocobaltate(III). Otherexamples of suitable double metal cyanide compounds can be found e.g. inU.S. Pat. No. 5,158,922 (column 8, lines 29-66). It is particularlypreferable to use zinc hexacyanocobaltate(HI).

The organic complexing ligands added in the preparation of the DMCcatalysts are disclosed e.g. in U.S. Pat. No. 5,158,922 (cf. especiallycolumn 6, lines 9 to 65), U.S. Pat. No. 3,404,109, U.S. Pat. No.3,829,505, U.S. Pat. No. 3,941,849, EP-A 700 949, EP-A 761 708, JP 4 145123, U.S. Pat. No. 5,470,813, EP-A 743 093 and WO-A 97/40086). Forexample, water-soluble organic compounds with heteroatoms, such asoxygen, nitrogen, phosphorus or sulfur, which can form complexes withthe double metal cyanide compound are used as organic complexingligands. Preferred organic complexing ligands are alcohols, aldehydes,ketones, ethers, esters, amides, ureas, nitriles, sulfides and mixturesthereof. Particularly preferred organic complexing ligands are aliphaticethers (such as dimethoxyethane), water-soluble aliphatic alcohols (suchas ethanol, isopropanol, n-butanol, isobutanol, sec-butanol,tert-butanol, 2-methyl-3-buten-2-ol and 2-methyl-3-butyn-2-ol), andcompounds comprising both aliphatic or cycloaliphatic ether groups andaliphatic hydroxyl groups (e.g. ethylene glycol mono-tert-butyl ether,diethylene glycol mono-tert-butyl ether, tripropylene glycol monomethylether and 3-methyl-3-oxetanemethanol). Very particularly preferredorganic complexing ligands are selected from one or more compounds fromthe group comprising dimethoxyethane, tert-butanol,2-methyl-3-buten-2-ol, 2-methyl-3-butyn-2-ol, ethylene glycolmono-tert-butyl ether and 3-methyl-3-oxetanemethanol.

Optionally, one or more complexing components from the following classesof compounds are used in the preparation of the DMC catalysts:polyethers, polyesters, polycarbonates, polyalkylene glycol sorbitanesters, polyalkylene glycol glycidyl ethers, polyacrylamide,poly(acrylamide-co-acrylic acid), polyacrylic acid, poly-(acrylicacid-co-maleic acid), polyacrylonitrile, polyalkyl acrylates, polyalkylmethacrylates, polyvinyl methyl ether, polyvinyl ethyl ether, polyvinylacetate, polyvinyl alcohol, poly-N-vinylpyrrolidone,poly(N-vinylpyrrolidone-co-acrylic acid), polyvinyl methyl ketone,poly(4-vinylphenol), poly(acrylic acid-co-styrene), oxazoline polymers,polyalkyleneimines, maleic acid and maleic anhydride copolymers,hydroxyethyl cellulose and polyacetals, or glycidyl ethers, glycosides,carboxylic acid esters of polyhydric alcohols, gallic acids or theirsalts, esters or amides, cyclodextrins, phosphorus compounds,α,β-unsaturated carboxylic acid esters or ionic surface-activecompounds.

Preferably, in the first step of the preparation of the DMC catalysts,the aqueous solution of the metal salt (e.g. zinc chloride), used instoichiometric excess (at least 50 mol %, based on the metal cyanidesalt, i.e. a molar ratio of metal salt to metal cyanide salt of at least2.25 to 1.00) is reacted with the aqueous solution of the metal cyanidesalt (e.g. potassium hexacyanocobaltate) in the presence of the organiccomplexing ligand (e.g. tert-butanol) to form a suspension comprisingthe double metal cyanide compound (e.g. zinc hexacyanocobaltate), water,excess metal salt and the organic complexing ligand.

The organic complexing ligand can be present in the aqueous solution ofthe metal salt and/or the aqueous solution of the metal cyanide salt, orit is added immediately to the suspension obtained after precipitationof the double metal cyanide compound. It has been found advantageous tomix the aqueous solutions of the metal salt and metal cyanide salt andthe organic complexing ligand with vigorous agitation. Optionally, thesuspension formed in the first step is then treated with anothercomplexing component, the latter preferably being used in a mixture withwater and organic complexing ligand. A preferred procedure for carryingout the first step (i.e. preparation of the suspension) involves the useof a mixing nozzle, particularly preferably a jet disperser as describedin WO-A 01/39883.

In the second step, the isolation of the solid (i.e. the precursor ofthe catalyst according to the invention) from the suspension is effectedby known techniques such as centrifugation or filtration.

In one preferred embodiment, the isolated solid is then washed, in athird process step, with an aqueous solution of the organic complexingligand (e.g. by resuspension and then re-isolation by filtration orcentrifugation). This makes it possible e.g. to remove water-solubleby-products, such as potassium chloride, from the catalyst. Preferably,the amount of organic complexing ligand in the aqueous wash solution isbetween 40 and 80 wt %, based on the total solution.

Optionally, another complexing component, preferably in the rangebetween 0.5 and 5 wt %, based on the total solution, is added to theaqueous wash solution in the third step.

It is moreover advantageous to wash the isolated solid more than once.Preferably, a first washing step (c-1) is carried out with an aqueoussolution of the unsaturated alcohol (e.g. by resuspension and thenre-isolation by filtration or centrifugation) in order e.g. to removewater-soluble by-products, such as potassium chloride, from the catalystaccording to the invention. Particularly preferably, the amount ofunsaturated alcohol in the aqueous wash solution is between 40 and 80 wt%, based on the total solution of the first washing step. In the otherwashing steps (c-2), either the first washing step is repeated one ormore times, preferably one to three times, or, preferably, a non-aqueoussolution, e.g. a mixture or solution of unsaturated alcohol and anothercomplexing component (preferably in the range between 0.5 and 5 wt %,based on the total amount of wash solution of step (c-2)), is used asthe wash solution and the solid is washed therewith one or more times,preferably one to three times.

The isolated and optionally washed solid is then dried, optionally afterpulverization, at temperatures generally of 20 to 100° C. and atpressures generally of 0.1 mbar to normal pressure (1013 mbar).

A preferred procedure for isolating the DMC catalysts according to theinvention from the suspension, by filtration, filter cake washing anddrying, is described in WO-A 01/80994.

Step (ii):

In step (ii) of a preferred embodiment of the invention, a mixture ofethylene oxide (EO) and propylene oxide (PO) is used as the mixture ofat least two different alkylene oxides, the molar ratio PO/EO used instep (ii) being from 15/85 to 60/40, preferably from 15/85 to 40/60.Preferably, the polyethercarbonate polyols resulting from step (ii),comprising a terminal mixed block of EO and PO, have a proportion ofprimary OH groups of 10 to 90 mol %, particularly preferably of 20 to 50mol %.

The mean length of the mixed blocks of at least two different alkyleneoxides, prepared in step (ii), is preferably 2.0 to 20.0 alkylene oxideunits, particularly preferably 2.5 to 10.0 alkylene oxide units, basedin each case on one OH group of the polyethercarbonate polyol.

Preferably, the polyethercarbonate polyols resulting from step (ii),comprising a mixed block at least two alkylene oxides, have a hydroxylnumber of 20 mg KOH/g to 80 mg KOH/g, particularly preferably of 25 mgKOH/g to 60 mg KOH/g.

Step (iii):

Optionally, the process according to the invention for the preparationof polyethercarbonate polyols can also comprise a third step, wherein

-   -   (iii) the chain of the polyethercarbonate polyol with terminal        mixed block, resulting from step (ii), is extended with an        alkylene oxide, preferably with propylene oxide or ethylene        oxide, particularly preferably with propylene oxide.

The mean length of a pure alkylene oxide block prepared in step (iii) ispreferably 2 to 30 alkylene oxide units, particularly preferably 5 to 18alkylene oxide units, based in each case on one OH group of thepolyethercarbonate polyol. The reaction according to step (iii) can becarried out e.g. in the presence of DMC catalysts or else in thepresence of acidic catalysts (such as BF₃) or basic catalysts (such asKOH or CsOH). Preferably, the reaction according to step (iii) iscarried out in the presence of a DMC catalyst.

Polyethercarbonate Polyols

The invention thus also provides polyethercarbonate polyols comprising aterminal mixed block of at least two alkylene oxides, preferably aterminal mixed block of ethylene oxide (EO) and propylene oxide (PO).Preferably, the molar ratio PO/EO is from 15/85 to 60/40, preferablyfrom 15/85 to 40/60. In a preferred embodiment of the invention, thepolyethercarbonate polyols comprising a terminal mixed block of EO andPO have a proportion of primary OH groups of 10 to 90 mol %,particularly preferably of 20 to 50 mol %. Preferably, the inventionprovides polyethercarbonate polyols comprising a terminal mixed block ofat least two alkylene oxides, characterized in that the mean length ofthe terminal mixed block of at least two different alkylene oxides isfrom 2.0 to 20.0 alkylene oxide units, particularly preferably from 2.5to 10.0 alkylene oxide units (based in each case on one OH group of thepolyethercarbonate polyol). The polyethercarbonate polyols according tothe invention comprising a mixed block of at least two alkylene oxideshave a hydroxyl number preferably of 20 mg KOH/g to 80 mg KOH/g,particularly preferably of 25 mg KOH/g to 60 mg KOH/g.

Optionally, these polyethercarbonate polyols according to the inventioncan comprise a pure alkylene oxide block at the end of the chain, saidblock consisting preferably of propylene oxide or ethylene oxide units,particularly preferably of propylene oxide units. The mean length ofsuch a pure alkylene oxide block at the end of the chain is preferably 2to 30 alkylene oxide units, particularly preferably 5 to 18 alkyleneoxide units, based in each case on one OH group of thepolyethercarbonate polyol.

Flexible Polyurethane Foams

Preferably, the invention provides a process for the production offlexible polyurethane foams with a gross density according to DIN EN ISO3386-1-98 in the range from ≧10 kg/m³ to ≦150 kg/m³, preferably from ≧20kg/m³ to ≦70 kg/m³, and a compressive strength according to DIN EN ISO3386-1-98 in the range from ≧0.5 kPa to ≦20 kPa (at 40% deformationafter 4^(th) cycle) by reacting component A (polyol formulation)comprising

-   -   A1 100 to 10 parts by weight, preferably 100 to 50 parts by        weight, particularly preferably 100 parts by weight (based on        the sum of the parts by weight of components A1 and A2), of        polyethercarbonate polyol having a mixed block of at least two        alkylene oxides at the end of the chain, characterized in that        the terminal mixed block comprises a mixture of propylene oxide        (PO) and ethylene oxide (EO) in a molar ratio PO/EO of 15/85 to        60/40,    -   A2 0 to 90 parts by weight, preferably 0 to 50 parts by weight        (based on the sum of the parts by weight of components A1 and        A2), of conventional polyether polyol, component A particularly        preferably being free of conventional polyether polyol,    -   A3 0.5 to 25 parts by weight, preferably 2 to 5 parts by weight        (based on the sum of the parts by weight of components A1 and        A2), of water and/or physical blowing agents,    -   A4 0.05 to 10 parts by weight, preferably 0.2 to 4 parts by        weight (based on the sum of the parts by weight of components A1        and A2), of auxiliary substances and additives such as        -   a) catalysts,        -   b) surface-active additives and        -   c) pigments or flame retardants, and    -   A5 0 to 10 parts by weight, preferably 0 to 5 parts by weight        (based on the sum of the parts by weight of components A 1 and        A2), of compounds having isocyanate-reactive hydrogen atoms with        a molecular weight of 62-399,        with component B comprising polyisocyanates,        the preparation taking place at an index of 50 to 250,        preferably of 70 to 130, particularly preferably of 75 to 115,        and        all the parts by weight of components A1 to A5 in the present        patent application being scaled so that the sum of the parts by        weight of components A1+A2 in the composition is 100.

Preferably, the polyethercarbonate polyol of component A1 is obtainableby the above-described preparative process according to the invention.

Component A1

The preparation of component A1 according to steps (i) and (ii) andaccording to optional step (iii) has already been illustrated above inconnection with the process for preparing the polyethercarbonatepolyols.

Component A2

The starting components of component A2 are conventional polyetherpolyols. In terms of the invention, conventional polyether polyols areunderstood as meaning compounds that are alkylene oxide additionproducts of starter compounds with Zerewitinoff-active hydrogen atoms,i.e. polyether polyols with a hydroxyl number according to DIN 53240 of≧15 mg KOH/g to ≦80 mg KOH/g, preferably of ≧20 mg KOH/g to ≦60 mgKOH/g.

Starter compounds with Zerewitinoff-active hydrogen atoms that are usedfor the conventional polyether polyols usually have functionalities of 2to 6, preferably of 3, and the starter compounds are preferablyhydroxy-functional. Examples of hydroxy-functional starter compounds arepropylene glycol, ethylene glycol, diethylene glycol, dipropyleneglycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, hexanediol,pentanediol, 3-methyl-1,5-pentanediol, 1,12-dodecanediol, glycerol,trimethylolpropane, triethanolamine, pentaerythritol, sorbitol, sucrose,hydroquinone, pyrocatechol, resorcinol, bisphenol F, bisphenol A,1,3,5-trihydroxybenzene, and condensation products of formaldehyde andphenol, melamine or urea which comprise methylol groups. It ispreferable to use glycerol and/or trimethylolpropane as the startercompound.

Examples of suitable alkylene oxides are ethylene oxide, propyleneoxide, 1,2-butylene oxide or 2,3-butylene oxide, and styrene oxide.Preferably, propylene oxide and ethylene oxide are added to the reactionmixture individually, as a mixture or successively. If the alkyleneoxides are metered in successively, the products prepared comprisepolyether chains with block structures. Products with ethylene oxideblocks are characterized e.g. by increased concentrations of primary endgroups, imparting an advantageous isocyanate reactivity to the systems.

Component A3

Water and/or physical blowing agents are used as component A3. Examplesof physical blowing agents used are carbon dioxide and/or highlyvolatile organic substances.

Component A4

Substances used as component A4 are auxiliary substances and additivessuch as

-   a) catalysts (activators),-   b) surface-active additives (surfactants) such as emulsifiers and    foam stabilizers, especially those with low emissions, e.g. products    of the Tegostab® LF series, and-   c) additives such as reaction retarders (e.g. acid-reacting    substances like hydrochloric acid or organic acid halides), cell    regulators (e.g. paraffins, fatty alcohols or    dimethylpolysiloxanes), pigments, dyestuffs, flame retardants (e.g.    tricresyl phosphate), ageing and weathering stabilizers,    plasticizers, fungistatic and bacteriostatic substances, fillers    (e.g. barium sulfate, kieselguhr, black or white chalk) and release    agents.

These auxiliary substances and additives that are optionally to be usedconcomitantly are described e.g. in EP-A 0 000 389, pages 18-21. Otherexamples of auxiliary substances and additives that are optionally to beused concomitantly according to the invention, and details of the modeof use and mode of action of these auxiliary substances and additives,are described in Kunststoff-Handbuch, volume VII, edited by G. Oertel,Carl-Hanser-Verlag, Munich, 3^(rd) edition, 1993, e.g. on pages 104-127.

Preferred catalysts are aliphatic tertiary amines (e.g. trimethylamine,tetramethyl-butanediamine), cycloaliphatic tertiary amines (e.g.1,4-diaza(2,2,2)bicyclooctane), aliphatic amino ethers (e.g.dimethylaminoethyl ether and N,N,N-trimethyl-N-hydroxyethylbisaminoethylether), cycloaliphatic amino ethers (e.g. N-ethyl-morpholine), aliphaticamidines, cycloaliphatic amidines, urea, urea derivatives (e.g.aminoalkylureas; cf., for example, EP-A 0 176 013, especially(3-dimethylamino-propylamine)urea) and tin catalysts (e.g. dibutyltinoxide, dibutyltin dilaurate, tin octanoate).

Particularly preferred catalysts are

-   α) urea, urea derivatives and/or-   (β) amines and amino ethers each comprising a functional group that    reacts chemically with the isocyanate. The functional group is    preferably a hydroxyl group or a primary or secondary amino group.    These particularly preferred catalysts have the advantage of    exhibiting a greatly reduced migration and emission behaviour.

The following may be mentioned as examples of particularly preferredcatalysts: (3-dimethylaminopropylamine)urea,2-(2-dimethylaminoethoxy)ethanol,N,N-bis-(3-dimethylaminopropyl)-N-isopropanolamine,N,N,N-trimethyl-N-hydroxyethyl-bisaminoethyl ether and3-dimethylaminopropylamine.

Component A5

Optionally, compounds used as component A5 have at least twoisocyanate-reactive hydrogen atoms and a molecular weight of 32 to 399.These are understood as meaning compounds having hydroxyl groups and/oramino groups and/or thiol groups and/or carboxyl groups, preferablycompounds having hydroxyl groups and/or amino groups, which serve aschain extenders or crosslinking agents. These compounds normally have 2to 8, preferably 2 to 4, isocyanate-reactive hydrogen atoms. Examples ofcompounds which can be used as component A5 are ethanol-amine,diethanolamine, triethanolamine, sorbitol and/or glycerol. Otherexamples of compounds of component A5 are described in EP-A 0 007 502,pages 16-17.

Component B

Suitable polyisocyanates are aliphatic, cycloaliphatic, araliphatic,aromatic and heterocyclic polyisocyanates such as those described e.g.by W. Siefken in Justus Liebigs Annalen der Chemie, 562, pages 75 to136, for example those of formula (IX):

Q(NCO)_(n)  (IX)

wheren=2-4, preferably 2-3, and

-   Q is an aliphatic hydrocarbon radical having 2-18 C atoms,    preferably 6-10 C atoms, a cycloaliphatic hydrocarbon radical having    4-15 C atoms, preferably 6-13 C atoms, or an araliphatic hydrocarbon    radical having 8-15 C atoms, preferably 8-13 C atoms.

Examples are polyisocyanates such as those described in EP-A 0 007 502,pages 7-8. Preferred polyisocyanates are normally those which arereadily available in industry, e.g. 2,4- and 2,6-toluoylene diisocyanateand any desired mixtures of these isomers (“TDI”);polyphenylpolymethylene polyisocyanates such as those prepared byaniline-formaldehyde condensation followed by phosgenation (“crudeMDI”); and polyisocyanates having carbodiimide groups, urethane groups,allophanate groups, isocyanurate groups, urea groups or biuret groups(“modified polyisocyanates”), especially modified polyisocyanatesderived from 2,4- and/or 2,6-toluoylene diisocyanate or from 4,4′-and/or 2,4′-diphenylmethane diisocyanate. Preferably, the polyisocyanateused is at least one compound selected from the group comprising 2,4-and 2,6-toluoylene diisocyanate, 4,4′-, 2,4′- and 2,2′-diphenylmethanediisocyanate, and polyphenylpolymethylene polyisocyanate (“polynuclearMDI”). Particularly preferably, the polyisocyanate used is a mixturecomprising 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethanediisocyanate and polyphenylpolymethylene polyisocyanate.

To produce the flexible polyurethane foams, the reactants are reacted bythe one-stage process known per se, often using mechanical devices, e.g.those described in EP-A 355 000. Details of processing devices which arealso suitable for the invention are described in Kunststoff-Handbuch,volume VII, edited by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich1993, e.g. on pages 139 to 265.

The flexible polyurethane foams can be produced as foam mouldings orfoam blocks. The invention therefore provides processes for theproduction of flexible polyurethane foams, the flexible polyurethanefoams produced by these processes, the flexible polyurethane foam blocksor flexible polyurethane foam mouldings produced by these processes, theuse of the flexible polyurethane foams for the production of mouldings,and the mouldings themselves. The flexible polyurethane foams obtainableaccording to the invention have e.g. the following applications:furniture upholstery, textile padding, mattresses, car seats, headsupports, arm rests, sponges and component parts.

The index indicates the percentage ratio of the amount of isocyanateactually used to the stoichiometric amount, i.e. the amount ofisocyanate (NCO) groups calculated for conversion of the OH equivalent.

index=[(amount of isocyanate used):(calculated amount ofisocyanate)]·100  (X)

EXAMPLES

The present invention is illustrated in greater detail with the aid ofthe following Examples, in which the materials and abbreviations usedhave the following meanings and sources of supply:

-   A2-1: a trifunctional polyether polyol with an OH number of 48 mg    KOH/g, prepared by the DMC-catalysed alkoxylation of glycerol with a    mixture of propylene oxide and ethylene oxide in proportions of    89/11, and with approx. 8 mol % of primary OH groups-   A4-1: Tegostab® B 2370, a preparation of organo-modified    polysiloxanes from Evonik Goldschmidt-   A4-2: Addocat® 108, an amine catalyst from Rheinchemie-   A4-3: Addocat®SO, a tin catalyst from Rheinchemie-   TDI-1: a mixture comprising 80 wt % of 2,4-toluoylene diisocyanate    and 20 wt % of 2,6-toluoylene diisocyanate, with an NCO content of    48.3 wt %-   TDI-2: a mixture comprising 65 wt % of 2,4-toluoylene diisocyanate    and 35 wt % of 2,6-toluoylene diisocyanate, with an NCO content of    48.3 wt %

The analyses were performed as follows:

Dynamic viscosity: MCR 51 rheometer from Anton Paar, corresponding toDIN

Hydroxyl number: according to standard DIN 53240

The gross density was determined according to DIN EN ISO 3386-1-98.

The compressive strength was determined according to DIN EN ISO3386-1-98 (at 40% deformation after 4^(th) cycle).

The tensile strength and elongation at break were determined accordingto DIN EN ISO 1798.

The proportion of CO₂ incorporated in the resulting polyethercarbonatepolyol was determined by ¹H-NMR (Bruker, DPX 400, 400 MHz, pulse programzg30, wait time d1:10 sec, 64 scans). All samples were dissolved indeuterated chloroform. The relevant resonances in the ¹H-NMR (relativeto TMS=0 ppm) are as follows: cyclic carbonate (formed as a by-product)with resonance at 4.5 ppm; carbonate (resulting from carbon dioxideincorporated in the polyethercarbonate polyol) with resonances at 5.1 to4.8 ppm; unreacted PO with resonance at 2.4 ppm; polyether polyol (i.e.without incorporated carbon dioxide) with resonances at 1.2 to 1.0 ppm;1,8-octanediol (incorporated as starter molecule (if present)) withresonance at 1.6 to 1.52 ppm.

The molar proportion of polymer-incorporated carbonate in the reactionmixture is calculated as below according to formula (XI), using thefollowing abbreviations:

F(4.5)=area of the resonance at 4.5 ppm for cyclic carbonate(corresponds to one H atom)F(5.1-4.8)=area of the resonance at 5.1-4.8 ppm for polyethercarbonatepolyol and one H atom for cyclic carbonateF(2.4)=area of the resonance at 2.4 ppm for free, unreacted POF(1.2-1.0)=area of the resonance at 1.2-1.0 ppm for polyether polyolF(1.6-1.52)=area of the resonance at 1.6 to 1.52 ppm for 1,8-octanediol(starter), if present

Taking the relative intensities into account, the polymer-boundcarbonate (“linear carbonate” LC) in the reaction mixture was convertedto mol % according to formula (XI) below:

$\begin{matrix}{{LC} = {\frac{{F\left( {5.1 - 4.8} \right)} - {F(4.5)}}{\begin{matrix}{{F\left( {5.1 - 4.8} \right)} + {F(2.4)} + {0.33*{F\left( {1.2 - 1.0} \right)}} +} \\{0.25*{F\left( {1.6 - 1.52} \right)}}\end{matrix}}*100}} & ({XI})\end{matrix}$

The proportion by weight (in wt %) of polymer-bound carbonate (LC′) inthe reaction mixture was calculated according to formula (XII):

$\begin{matrix}{{LC}^{\prime} = {\frac{\left\lbrack {{F\left( {5.1 - 4.8} \right)} - {F(4.5)}} \right\rbrack*102}{N}*100\%}} & ({XII})\end{matrix}$

the value of N (“denominator” N) being calculated according to formula(XIII):

N═[F(5.1−4.8)−F(4.5)]*102+F(4.5)*102+F(2.4)*58+0.33*F(1.2−1.0)*58+0.25*F(1.6−1.52)*146  (XIII)

The factor 102 results from the sum of the molecular weights of CO₂(molecular weight 44 g/mol) and propylene oxide (molecular weight 58g/mol), the factor 58 results from the molecular weight of propyleneoxide and the factor 146 results from the molecular weight of the1,8-octanediol starter used (if present).

The proportion by weight (in wt %) of cyclic carbonate (CC′) in thereaction mixture was calculated according to formula (XIV):

$\begin{matrix}{{CC}^{\prime} = {\frac{{F(4.5)}*102}{N}*100\%}} & ({XIV})\end{matrix}$

the value of N being calculated according to formula (XIII).

To calculate the composition based on the polymer component (consistingof polyether polyol, synthesized from starter and propylene oxide duringthe activation steps taking place under CO₂-free conditions, andpolyethercarbonate polyol, synthesized from starter, propylene oxide andcarbon dioxide during the activation steps taking place in the presenceof CO₂ and during copolymerization) from the values of the compositionof the reaction mixture, the non-polymer constituents of the reactionmixture (i.e. cyclic propylene carbonate and any unreacted propyleneoxide present) were arithmetically eliminated. The proportion by weightof carbonate repeating units in the polyethercarbonate polyol wasconverted to a proportion by weight of carbon dioxide by means of thefactor F=44/(44+58). The data for the CO₂ content of thepolyethercarbonate polyol are normalized to the proportion of thepolyethercarbonate polyol molecule formed during the copolymerizationand optionally the activation steps in the presence of CO₂ (i.e. theproportion of the polyethercarbonate polyol molecule resulting from thestarter (1,8-octanediol, if present) and from the reaction of thestarter with epoxide, added under CO₂-free conditions, was not takeninto account here).

Determination of the molar proportion of primary OH groups: by ¹H-NMR(Bruker DPX 400, deuterochloroform):

To determine the content of primary OH groups, the polyethercarbonatesamples were first peracetylated.

The following peracetylation mixture was prepared for this purpose:

-   -   9.4 g of acetic anhydride p.a.    -   1.6 g of acetic acid p.a.    -   100 ml of pyridine p.a.

For the peracetylation reaction 10 g of polyethercarbonate polyol wereweighed into a 300 ml ground-glass Erlenmeyer flask. The volume ofperacetylation mixture depended on the OH number of thepolyethercarbonate to be peracetylated, the OH number of thepolyethercarbonate polyol being rounded to the nearest tens digit (basedin each case on 10 g of polyethercarbonate polyol); 10 ml ofperacetylation mixture are then added per 10 mg KOH/g. Accordingly, forexample, 50 ml of peracetylation mixture were added to the 10 g sampleof polyethercarbonate polyol with an OH number of 45.1 mg KOH/g.

After the addition of glass boiling beads, the ground-glass Erlenmeyerflask was provided with a riser tube (air condenser) and the sample wasboiled for 75 min under gentle reflux. The sample mixture was thentransferred to a 500 ml round-bottom flask and volatile constituents(essentially pyridine, acetic acid and excess acetic anhydride) weredistilled off over a period of 30 min at 80° C. and 10 mbar (absolute).The distillation residue was then treated with 3×100 ml of cyclohexane(toluene was used as an alternative in cases where the distillationresidue did not dissolve in cyclohexane) and volatile constituents wereremoved for 15 min at 80° C. and 400 mbar (absolute). Volatileconstituents were then removed from the sample for one hour at 100° C.and 10 mbar (absolute).

To determine the molar proportions of primary and secondary OH endgroups in the polyethercarbonate polyol, the sample prepared as abovewas dissolved in deuterated chloroform and analysed by ¹H-NMR (Bruker,DPX 400, 400 MHz, pulse program zg30, wait time dl: 10 sec, 64 scans).The relevant resonances in the ¹H-NMR (relative to TMS=0 ppm) are asfollows:

methyl signal of a peracetylated secondary OH end group: 2.04 ppmmethyl signal of a peracetylated primary OH end group: 2.07 ppm

The molar proportion of secondary and primary OH end groups is thenworked out as follows:

proportion of secondary OH end groups(CH—OH)═F(2.04)/(F(2.04)+F(2.07))*100%  (XV)

proportion of primary OH end groups(CH₂—OH)═F(2.07)/(F(2.04)+F(2.07))*100%  (XVI)

In formulae (XV) and (XVI) F represents the area of the resonance at2.04 ppm or 2.07 ppm.

I. Preparation of Polyethercarbonate Polyol A1-1 by Copolymerization ofPO and CO₂

140 mg of DMC catalyst (prepared according to Example 6 of WO-A01/80994) and 160 g of an anhydrous trifunctional poly(oxypropylene)polyol with an OH number of 235 mg KOH/g were placed as H-functionalstarter substances in a 1 litre pressurized reactor fitted with a withgas metering device. The reactor was heated to 130° C. and renderedinert by the repeated application of nitrogen to approx. 5 bar andsubsequent pressure release to approx. 1 bar. This process was carriedout 3 times. 25 g of propylene oxide (PO) were rapidly metered into thereactor at 130° C. and in the absence of CO₂. The start of the reactionwas signalled by a hotspot and by a pressure drop to roughly the initialvalue (approx. 1 bar). After the first pressure drop 20 g of PO and then19 g of PO were rapidly metered in, each time causing a further hotspotand pressure drop. After 50 bar of CO₂ had been applied to the reactor,50 g of PO were rapidly metered in, causing a hotspot after a furtherwait time. The carbon dioxide (CO₂) pressure started to drop at the sametime. The pressure was regulated in such a way that fresh CO₂ was addedwhen the pressure dropped below the set value. Only then was theremaining propylene oxide (387 g) pumped continuously into the reactorat approx. 1.8 g/min; after 10 minutes the temperature was lowered to105° C. in steps of 5° C. every five minutes. When the addition of POwas complete, stirring (1500 rpm) was continued for a further 60 minutesat 105° C. and the pressure indicated above. Finally, highly volatileconstituents were separated from the product by film evaporation.

Analysis of the Resulting Polyethercarbonate Polyol A1-1:

Hydroxyl number: 54.9 mg KOH/gDynamic viscosity: 4115 mPas (25° C.)Content of incorporated CO₂: 12.8 wt %II. Preparation of Polyethercarbonate Polyols with Terminal AlkyleneOxide Block Preparation of Polyethercarbonate Polyol A1-2 (PO/EO=100/0[mol/mol]) (Comparison)

403 g of polyethercarbonate polyol A1-1 were placed in a 2 l laboratoryautoclave under a nitrogen atmosphere, heated to 130° C. and thenstripped with nitrogen at this temperature for 30 minutes at a pressureof 0.1 bar (absolute). 68.8 g (1.184 mol) of PO were then metered intothe reactor at 130° C. over a period of 5 minutes, with stirring. Aftera post-reaction time of 90 minutes, highly volatile constituents wereremoved by heating at 90° C. for 30 minutes under vacuum and thereaction mixture was then cooled to room temperature.

Analysis of the resulting polyethercarbonate polyol A1-2:Hydroxyl number: 47.3 mg KOH/gDynamic viscosity: 3130 mPas (25° C.)Content of primary OH groups: 8 mol %Preparation of Polyethercarbonate Polyol A1-3 (PO/EO=70/30 [mol/mol])(Comparison)

385 g of polyethercarbonate polyol A1-1 were placed in a 2 l laboratoryautoclave under a nitrogen atmosphere, heated to 130° C. and thenstripped with nitrogen at this temperature for 30 minutes at a pressureof 0.1 bar (absolute). A mixture of 46.1 g (0.793 mol) of PO and 15.0 g(0.340 mol) of EO was then metered into the reactor at 130° C. over aperiod of 5 minutes, with stirring. After a post-reaction time of 90minutes, highly volatile constituents were removed by heating at 90° C.for 30 minutes under vacuum and the reaction mixture was then cooled toroom temperature.

Analysis of the Resulting Polyethercarbonate Polyol A1-3:

Hydroxyl number: 45.1 mg KOH/gDynamic viscosity: 3735 mPas (25° C.)Content of primary OH groups: 21 mol %Preparation of Polyethercarbonate Polyol A1-4 (PO/EO=50/50 [mol/mol])

310 g of polyethercarbonate polyol A1-1 were placed in a 2 l laboratoryautoclave under a nitrogen atmosphere, heated to 130° C. and thenstripped with nitrogen at this temperature for 30 minutes at a pressureof 0.1 bar (absolute). A mixture of 26.4 g (0.454 mol) of PO and 20.1 g(0.456 mol) of EO was then metered into the reactor at 130° C. over aperiod of 5 minutes, with stirring. After a post-reaction time of 90minutes, highly volatile constituents were removed by heating at 90° C.for 30 minutes under vacuum and the reaction mixture was then cooled toroom temperature.

Analysis of the resulting polyethercarbonate polyol A1-4:Hydroxyl number: 44.7 mg KOH/gDynamic viscosity: 4380 mPas (25° C.)Content of primary OH groups: 29 mol %Preparation of Polyethercarbonate Polyol A1-5 (PO/EO=30/70 [mol/mol])401 g of polyethercarbonate polyol A1-1 were placed in a 2 l laboratoryautoclave under a nitrogen atmosphere, heated to 130° C. and thenstripped with nitrogen at this temperature for 30 minutes at a pressureof 0.1 bar (absolute). A mixture of 22.5 g (0.387 mol) of PO and 39.8 g(0.902 mol) of EO was then metered into the reactor at 130° C. over aperiod of 5 minutes, with stirring. After a post-reaction time of 90minutes, highly volatile constituents were removed by heating at 90° C.for 30 minutes under vacuum and the reaction mixture was then cooled toroom temperature.Analysis of the resulting polyethercarbonate polyol A1-5:Hydroxyl number: 47.5 mg KOH/gDynamic viscosity: not determinable at 25° C. as A1-5 is a solidContent of primary OH groups: 37 mol %Preparation of Polyethercarbonate Polyol A1-6 (PO/EO=0/100 [mol/mol])(comparison

401 g of polyethercarbonate polyol A1-1 were placed in a 2 l laboratoryautoclave under a nitrogen atmosphere, heated to 130° C. and thenstripped with nitrogen at this temperature for 30 minutes at a pressureof 0.1 bar (absolute). 56.8 g (1.288 mol) of EO were then metered intothe reactor at 130° C. over a period of 5 minutes, with stirring. Aftera post-reaction time of 90 minutes, highly volatile constituents wereremoved by heating at 90° C. for 30 minutes under vacuum and thereaction mixture was then cooled to room temperature.

Analysis of the resulting polyethercarbonate polyol A1-6:Hydroxyl number: 47.3 mg KOH/gDynamic viscosity: not determinable at 25° C. as A1-6 is a solidContent of primary OH groups: 53 mol %

III. Production of Flexible Polyurethane Foam Blocks

The starting materials listed in the Examples in Table 1 below werereacted together according to the processing method conventionally usedfor the production of polyurethane foams by the one-stage process.

Surprisingly, the flexible polyurethane foam blocks according to theinvention (Examples 4 to 6), in which polyethercarbonate polyols with aterminal mixed block of propylene oxide (PO) and ethylene oxide (EO) ina molar ratio PO/EO of 15/85 to 60/40 were processed, exhibited a highercompressive strength and a higher tensile strength than flexible foamblocks based on a polyether polyol (A2-1; cf. Table 1, ComparativeExample 1) or on a polyethercarbonate polyol with a terminal propyleneoxide block (A1-2; cf. Table 1, Comparative Example 2). Advantageousproperties in respect of compressive strength were achieved withpolyethercarbonate polyols with a terminal mixed block having a ratioPO/EO of 50/50 or 30/70 (A1-4 or A1-5; cf. Table 1, Examples 4, 5 and6). Particularly advantageous properties in respect of compressivestrength and tensile strength were achieved with a polyethercarbonatepolyol with a terminal mixed block having a ratio PO/EO of 30/70 (A1-5;cf. Table 1, Examples 5 and 6).

TABLE 1 Production and properties of the flexible polyurethane foamblocks 1 2 3 7 (Comp.) (Comp.) (Comp.) 4 5 6 (Comp.) Component A A2-1[pbw] 94.95 A1-2 [pbw] 94.95 A1-3 [pbw] 94.95 A1-4 [pbw] 94.98 A1-5[pbw] 94.97 94.97 A1-6 [pbw] 94.97 Water [pbw] 3.80 3.80 3.80 3.80 3.803.80 3.80 A4-1 [pbw] 0.95 0.95 0.95 0.95 0.95 0.95 0.95 A4-2 [pbw] 0.110.11 0.11 0.11 0.11 0.11 0.11 A4-3 [pbw] 0.19 0.19 0.19 0.15 0.17 0.170.17 Component B TDI-1 [pbw] 100 100 90 100 100 80 100 TDI-2 [pbw] 10 20WR (A:B) 100: 47.27 47.27 47.27 47.27 47.27 47.27 47.27 Index 108 108108 108 108 108 108 Gross density [kg/m³] 27.5 28.9 31.5 30.5 27.9 27.924.2 Compressive [kPa] 4.8 5.7 6.4 6.8 7.6 7.3 5.5 strength Tensilestrength [kPa] 85 79 104 99 107 113 96 Elongation at [%] 123 103 114 9796 110 104 break Abbreviations: Comp. = Comparative Example; pbw = partsby weight; WR (A:B) = weight ratio of component A to component B at theindicated index, based on 100 parts by weight of component A

1-15. (canceled)
 16. A process for the preparation of apolyethercarbonate polyol, comprising (i) preparing, in a first step, apolyethercarbonate polyol chain from one or more H-functional startersubstances, one or more alkylene oxides and carbon dioxide in thepresence of at least one DMC catalyst, and (ii) extending, in a secondstep, the polyethercarbonate polyol chain with a mixture of at least twodifferent alkylene oxides in the presence of at least one DMC catalyst,and in that the mixture of at least two different alkylene oxides in thesecond step (ii) is a mixture comprising propylene oxide (PO) andethylene oxide (EO) in a molar ratio PO/EO of 15/85 to 60/40.
 17. Theprocess according to claim 16, wherein, in the first step (i), (α) theH-functional starter substance or a mixture of at least two H-functionalstarter substances is taken and optionally water and/or other highlyvolatile compounds are removed by raising the temperature and/orreducing the pressure (“drying”), the DMC catalyst being added to theH-functional starter substance or the mixture of at least twoH-functional starter substances before or after drying, (β) foractivation, a fraction, based on the total amount of alkylene oxidesused in the activation and copolymerization, of one or more alkyleneoxides is added to the mixture resulting from step (α), optionally, thealkylene oxide fraction is added in the presence of CO₂, the hotspotthat occurs due to the subsequent exothermic chemical reaction and/or apressure drop in the reactor then being allowed to subside, andoptionally, the activation step (β) is be carried out several times, and(γ) one or more alkylene oxides and carbon dioxide are added to themixture resulting from step (β), wherein the alkylene oxide in step (γ)is identical or different from the alkylene oxide used in step (β). 18.The process according to claim 16, wherein the mixture of at least twodifferent alkylene oxides used in the second step (ii) is a mixtureconsisting of propylene oxide (PO) and ethylene oxide (EO) in a molarratio PO/EO of 15/85 to 60/40.
 19. The process according to claim 16,wherein, in the second step (ii), the molar ratio of propylene oxide(PO) to ethylene oxide (EO) is from 15/85 to 40/60.
 20. The processaccording to claim 16, further comprising (iii) extending thepolyethercarbonate polyol chain with terminal mixed block, resultingfrom step (ii), with an alkylene oxide.
 21. A polyethercarbonate polyolcomprising a terminal mixed block of at least two alkylene oxides,wherein the terminal mixed block comprises a mixture of propylene oxide(PO) and ethylene oxide (EO) in a molar ratio PO/EO of 15/85 to 60/40.22. The polyethercarbonate polyol according to claim 21, wherein theterminal mixed block consists of a mixture of propylene oxide (PO) andethylene oxide (EO) in a molar ratio PO/EO of 15/85 to 60/40.
 23. Thepolyethercarbonate polyol according to claim 21, wherein the molar ratioof propylene oxide (PO) to ethylene oxide (EO) in the mixed block isfrom 15/85 to 40/60.
 24. The polyethercarbonate polyol according toclaim 21, wherein the chain of the terminal mixed block is extended withan alkylene oxide.
 25. The polyethercarbonate polyol according to claim21, wherein the mean length of the terminal mixed block of at least twodifferent alkylene oxides is from 2.0 to 20.0 alkylene oxide units. 26.A process for the production of a flexible polyurethane foam comprisingutilizing a polyol comprising the polyethercarbonate polyol according toclaim 21 as component A.
 27. The process for the production of aflexible polyurethane foam with a gross density according to DIN EN ISO3386-1-98 in the range from ≧10 kg/m3 to ≦150 kg/m3 and a compressivestrength according to DIN EN ISO 3386-1-98 in the range from ≧0.5 kPa to≦20 kPa, at 40% deformation after 4th cycle, by reacting component Acomprising A1 100 to 10 parts by weight, based on the sum of the partsby weight of components A₁ and A2, of polyethercarbonate polyolaccording to claims 21, A2 0 to 90 parts by weight, based on the sum ofthe parts by weight of components A1 and A2, of conventional polyetherpolyol, A3 0.5 to 25 parts by weight, based on the sum of the parts byweight of components A1 and A2, of water and/or physical blowing agents,A4 0.05 to 10 parts by weight, based on the sum of the parts by weightof components A1 and A2, of an auxiliary substance and/or an additive,and A5 0 to 10 parts by weight, based on the sum of the parts by weightof components A1 and A2, of compounds having isocyanate-reactivehydrogen atoms with a molecular weight of 62-399, with component Bcomprising a polyisocyanate, the preparation taking place at an index of50 to 250, and all the parts by weight of components A1 to A5 in thepresent patent application being scaled so that the sum of the parts byweight of components A1+A2 in the composition is
 100. 28. The processaccording to claim 27 wherein component A consists of A1 100 parts byweight of polyethercarbonate polyol according to claim 21, A2 0 parts byweight of conventional polyether polyol, A3 0.5 to 25 parts by weight(based on the parts by weight of component A1) of water and/or physicalblowing agents, A4 0.05 to 10 parts by weight (based on the parts byweight of component A1) of an auxiliary substances and/or an additive,and A5 0 to 10 parts by weight (based on the parts by weight ofcomponent A1) of compounds having isocyanate-reactive hydrogen atomswith a molecular weight of 62-399.
 29. The process for the production ofa flexible polyurethane foam comprising utilizing a polyol component(component A) which comprises a polyethercarbonate polyol obtainedaccording to claim
 16. 30. A flexible polyurethane foam with a grossdensity according to DIN EN ISO 3386-1-98 in the range from ≧10 kg/m³ to≦150 kg/m³ and a compressive strength according to DIN EN ISO 3386-1-98in the range from ≧0.5 kPa to ≦20 kPa, at 40% deformation after 4^(th)cycle, obtained by the process according to claim 26.